Vapor Emission Control Fuel Cap

ABSTRACT

A fuel tank assembly with a fuel cap sub-assembly that includes active (that is, automatic) pressure equalization hardware and a passive (that is, manually operated) vent. The fuel cap assembly further includes radially oriented ratchet teeth. The fuel cap assembly further includes single piece fuel cap tether that is anchored in the interior space of the fuel tank.

RELATED APPLICATION

The present application claims priority to U.S. provisional patent application No. 61/318,842, filed on Mar. 30, 2010; all of the foregoing patent-related document(s) are hereby incorporated by reference herein in their respective entirety(ies).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel tank assemblies, more particularly to fuel tank assembly for marine vehicles and even more particularly to fuel cap sub-assemblies for fuel tank assemblies for marine vehicles.

2. Description of the Related Art

FIG. 1 shows convention fuel tank assembly 100 for a marine vehicle (not shown), such as a ship or boat. Assembly 100 includes: tank 102; liquid fuel 104; cap sub-assembly 108; fuel out sub-assembly 110 and closeable vapor vent 112. In the interior space of the tank, located above the liquid fuel is vapor space 106. As is understood in the prior art, when this vapor space is closed off, by sealing the tank in a pressure tight fashion, from the exterior atmosphere, then the vapor space may develop a positive pressure or a negative pressure with respect to atmospheric pressure. For example, if the tank is sealed and the temperature warms, then the liquid fuel will evaporate into the vapor space to a greater extent and cause the pressure in the vapor space to rise above the atmospheric pressure, thereby developing a positive pressure. As a further example, if the tank is sealed and liquid fuel is removed from the tank through the fuel out sub-assembly (for example, to fuel a propulsion engine in the marine vehicle), then the vapor space will tend to develop a negative pressure.

Closeable vapor vent 112 is a prior art solution used to deal with the interrelated issues of tank sealing and positive/negative pressure differences. More specifically, it is often desired to seal the tank in a pressure tight manner so that liquid fuel and/or fuel vapor does not escape the tank. For example, if the fuel in the tank will not be used for a long period, then it is generally desirable to seal the tank to avoid loss of fuel by evaporation to the atmosphere. On the other hand, if the tank is sealed then positive or negative pressures can develop and cause problems. For example, if there is a positive pressure in the vapor space, then the fuel cap may become difficult to remove and/or liquid fuel may spray out of the tank when the cap is removed to unseal the tank. As a further example, if the tank is sealed when the fuel is being used to fuel an engine, then a negative pressure may develop and cause the engine to malfunction due to the increasing difficulty of sucking fuel out of the tank against the increasing negative pressure.

Closeable vapor vent 112 is a passive device that allows a user to prevent and/or deal with positive or negative pressures. The closable vapor vent allows the user to unseal the tank in a carefully controlled manner so that air/vapor in the vapor space can exchange with air of the outside atmosphere. In other words, when the closeable vapor vent is closed by a user (and the cap is on), then the tank is sealed. When the closeable vapor vent is opened by a user, then the tank is unsealed. If there exists a pressure difference at the time the user opens the closeable vapor vent, then the pressure difference can be equalized smoothly and slowly to prevent adverse consequences, such as the spraying of fuel. If the user leaves the vent open (for example, during periods when the fuel is being consumed), then pressure differences will not develop. If the user closes the vent (for example, when the marine vehicle is in storage), then fuel will not be lost to the atmosphere, and any pressure difference can be dealt with by carefully opening the vent before using the marine vehicle again.

Although closeable vapor vent 112 is separate from cap 108 in fuel tank assembly 100, it is noted that in some conventional marine vehicle fuel tank assemblies, the closeable vapor vent and cap are formed together as a single sub-assembly.

As mentioned above, the closeable vapor vent of assembly 100 is a passive pressure equalization device because it relies on the user to decide when it is best to have the vent in the open position and when to have the vent in the closed position. However, it has been recognized that this reliance on the user can lead to problems when the user lacks knowledge or judgement or is forgetful. In response to this problem, another conventional marine vehicle fuel tank assembly 200, as shown in FIG. 2, has been developed. Assembly 200 includes tank 202; liquid fuel 204; cap sub-assembly 208; fuel out sub-assembly 210; air intake valve 214; and vapor exhaust valve 216. In assembly 200, vapor space 206 is generally sealed, except: (i) if a negative pressure goes below some threshold, then the air intake valve automatically opens temporarily to allow external, atmospheric air to flow into the vapor space to equalize the pressure (or at least decrease the negative pressure somewhat); and (ii) if a positive pressure goes above some threshold, then the vapor exhaust valve automatically opens temporarily to allow vapor from the vapor space to flow out of the tank to equalize the pressure (or at least decrease the positive pressure somewhat). Assembly 200 is “active” in the sense that no user intervention is required.

Although air intake valve 214 and vapor exhaust valve 216 are each separate from cap assembly 208 in fuel tank assembly 200, it is noted that in some conventional marine vehicle fuel tank assemblies, one (or both) valves and that cap are formed together as a single sub-assembly.

The following publications may be prior art and may be of interest: (i) US patent (“USP”) U.S. Pat. No. 4,265,752 (“O'Banion”); (ii) U.S. Pat. No. 5,242,072 (“Koebernik”); (iii) U.S. Pat. No. 4,922,954 (“Blomquist”); (iv) U.S. Pat. No. 4,666,058 (“058 Harris”); (v) U.S. Pat. No. 4,787,529 (“529 Harris”); (vi) U.S. Pat. No. 5,116,257 (“Szlaga”); (vii) U.S. Pat. No. 4,498,493 (“493 Harris”); (viii) U.S. Pat. No. 5,108,001 (“001 Harris”); (ix) U.S. Pat. No. 6,886,597 (“Dragoni”); (x) U.S. Pat. No. 4,696,409 (“Vize”); and (xi) U.S. Pat. No. 4,796,777 (“Keller”).

Description of the Related Art Section Disclaimer: To the extent that specific publications are discussed above in this Description of the Related Art Section, these discussions should not be taken as an admission that the discussed publications (for example, published patents) are prior art for patent law purposes. For example, some or all of the discussed publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific publications are discussed above in this Description of the Related Art Section, they are all hereby incorporated by reference into this document in their respective entirety(ies).

BRIEF SUMMARY OF THE INVENTION

At least some embodiments according to one aspect of the present invention are directed to a fuel tank assembly that includes both of: (i) a passive, closeable vent; and (ii) active, automatic pressure equalization hardware (for example, an air intake valve and/or a vapor exhaust valve). In at least some embodiments according to this aspect of the present invention, the closeable vent is biased in the closed position. The closeable vent and/or the pressure equalization hardware are preferably built into the cap assembly.

According to a further aspect of the present invention, a fuel cap assembly: (i) defines a central axis, an axial direction, an angular direction and a radial direction; (ii) includes a fuel cap that is rotatable in the angular direction about the central axis; (iii) includes multiple ratchet teeth and ratchet tooth engagement hardware; and (iv) with the ratchet teeth extending and engaging with the ratchet tooth engagement hardware in the radial direction.

According to a further aspect of the present invention, a fuel cap assembly includes: (i) a removable fuel cap; (ii) a one piece tether member; and (iii) the fuel cap and tether assembly are sized and shaped so that the tether member locks into the removable fuel cap.

Various embodiments of the present invention may exhibit one or more of the following objects, features and/or advantages:

(i) use of both active and passive hardware to equalize fuel tank pressure allows the active hardware to be used to accommodate relatively large pressure differences (positive and/or negative), while the passive hardware allows a user to have the option of accommodating pressure differences smaller than those required to trigger the active hardware;

(ii) more refined and granular control of fuel tank pressure;

(iii) decreases probability that fuel will spray out of tank and/or end up in the environment;

(iv) reduces probability that that tethered fuel cap will be lost;

(v) reduces cost and/or complexity of tethered fuel cap; and

(vi) more space-efficient ratcheted fuel cop; and/or

(vii) reduces cost and/or complexity of ratcheted fuel cap.

According to an aspect of the present invention, a fuel tank assembly includes: a fuel tank (defining an interior space), a passive vent and active pressure equalization hardware. The passive vent is movable between: (i) an open position that opens a first air communication path between the interior space of the fuel tank and the external atmosphere, and (ii) a closed position that closes the first air communication path. The active pressure equalization hardware automatically and selectively opens at least a second air communication paths in response to a pressure difference between the interior space of the fuel tank and the eternal atmosphere.

According to another aspect of the present invention, a fuel cap assembly includes: a removable fuel cap; and fuel cap receiving hardware. The removable fuel cap includes a first cap member and a second cap member. The fuel cap receiving hardware is connected, shaped and/or located to removably engage the removable fuel cap. The removable fuel cap defines a central axis, an axial direction, an angular direction and a radial direction. The removable fuel cap and fuel cap receiving hardware are connected, shaped and/or located so that the removable fuel cap is removed by turning it in the angular direction and translating it in the axial direction. The first cap member includes a plurality of ratchet teeth. The second cap member includes at least one ratchet tooth engaging member. The plurality of ratchet teeth face and engage with the at least one ratchet tooth engaging member in the radial direction.

According to another aspect of the present invention, a fuel cap assembly is designed for use with a fuel tank. The fuel cap assembly includes: a fuel cap; and a tether member (made of a single piece of a single material). The tether member includes a cap-securement portion that is shaped, sized and/or located to be mechanically secured to the fuel cap. The tether member further includes a tethering portion that is shaped, sized and/or located to: (i) be accommodated within an interior space of the fuel tank when the fuel cap is engaged to seal the fuel tank, and (ii) to tether the fuel cap at location(s) spaced apart from a fueling opening in the fuel tank when the fuel cap is removed from the fuel tank for fueling. The tether member further includes an anchor portion sized, shaped and/or located to be held within the interior space of the fuel tank, and prevented by physical interference from exiting the interior space of the fuel tank through the fueling opening.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings (cross-hatching may be omitted on cross-section views for clarity of illustration purposes), in which:

FIG. 1 is a schematic view of a prior art fuel tank assembly;

FIG. 2 is a schematic view of another prior art fuel tank assembly;

FIG. 3 is a schematic view of a first embodiment of a fuel tank assembly according to the present invention;

FIG. 4 is a schematic view of a second embodiment of a fuel tank assembly according to the present invention; and

FIG. 5 is a cross section view of a portion of a first embodiment of cap sub-assembly of the second embodiment fuel tank assembly;

FIG. 6 is a perspective view of a component of the first embodiment cap assembly;

FIG. 7 is a perspective view of a portion of the first embodiment cap sub-assembly;

FIG. 8 is a perspective view of a portion of the first embodiment cap sub-assembly;

FIG. 9 is a perspective view of a portion of the first embodiment cap sub-assembly;

FIG. 10 is a perspective view of a portion of the first embodiment cap sub-assembly;

FIG. 11 is a perspective view of a portion of the first embodiment cap sub-assembly;

FIG. 12 is a perspective view of a portion of the first embodiment cap sub-assembly;

FIG. 13 is a perspective view of a second embodiment cap sub-assembly suitable for use in the first embodiment fuel tank assembly;

FIG. 14 is a perspective view of a portion of the second embodiment cap sub-assembly;

FIG. 15 is a perspective view of a portion of the second embodiment cap sub-assembly;

FIG. 16 is a cross section view of a portion of the second embodiment cap sub-assembly;

FIG. 17 is a perspective view of a portion of the second embodiment cap sub-assembly;

FIG. 18 is a perspective view of a portion of the second embodiment cap sub-assembly;

FIG. 19 is a perspective view of a portion of the second embodiment cap sub-assembly;

FIG. 20 is a cross section view of a portion of the second embodiment cap sub-assembly;

FIG. 21 is a cross section view of a portion of the second embodiment cap sub-assembly; and

FIG. 22 is a perspective view of a portion of the second embodiment cap sub-assembly.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 shows fuel tank assembly 300 for a marine vehicle (not shown), such as a ship or boat. Assembly 300 includes: tank 302; liquid fuel 304; cap sub-assembly 308; fuel out sub-assembly 310; active pressure equalization hardware 315; and passive, biased-closed vent 350. In the interior space of the tank, located above the liquid fuel is vapor space 306. In this embodiment, the active pressure equalization hardware actively equalizes positive and/or negative vapor space pressure that goes above a certain positive pressure threshold and/or negative pressure threshold. In other words, the pressure equalization hardware may automatically respond to only positive pressure, only negative pressure or both positive and negative pressure. In variations where the pressure equalization hardware actively responds to both positive and negative pressure, the positive and negative pressure thresholds may or may not have the same magnitude. The active hardware may use automatic valve(s) or any other suitable active pressure equalizing hardware now known, or to be developed in the future. In variations where the pressure equalization hardware actively responds to both positive and negative pressure, the air communication path may or may not be the same for positive and negative pressure equalizations. For example, in embodiments where the pressure equalization hardware includes a separate air intake valve and vapor exhaust valve, the air communication paths will be different for active positive and negative pressure adjustments.

FIG. 4 shows fuel tank assembly 400 for a marine vehicle (not shown), such as a ship or boat. Assembly 400 includes: tank 402; liquid fuel 404; cap sub-assembly 408; and fuel out sub-assembly 410. Cap sub-assembly 408 includes air intake valve 414; vapor exhaust valve 416; and biased closed vent 450. In the interior space of the tank, located above the liquid fuel is vapor space 406. In assembly 400, the air intake valve and the vapor exhaust valve provide active pressure equalization. In assembly 400, the biased closed vent is a passive vent which is operated by a user. More specifically, the user can hold the biased closed vent in an open position to allow the pressure in the vapor space to equalize to atmospheric pressure. Because the vent is biased closed, the vent will return to a closed position, to seal the tank, when a user is not holding it open. Assembly 400 allows relatively large positive or negative pressure differences to be equalized automatically, but also allows a user to equalize smaller pressure differences that are not sufficiently large to automatically open the valve(s).

The operation of fuel cap assembly 408 will now be discussed in more detail in connection with FIGS. 5 to 12. As shown in FIGS. 5 to 12, fuel cap assembly 408 includes: outer shell member 408 a; inner shell member 408 b; tether member 408 c; housing portion 455 (of inner shell member); containment piece engagement portion 456 (of inner shell member); containment piece 458; first spring 460; elastomer ball 462; second spring 464; first slot channels 466 (defined in manual release button member); manual release button member 468; elastomer ball prod portion 470 (of the manual release button member); flange 472; second slot channels 474 (defined in manual release button member); ratchet teeth 475 (of the inner shell member); tether engagement slot 476 (of the inner shell member); tether-to-cap securing portion 480 (of the tether member); tethering leash portion 481 (of the tether member); anchor portion 482 (of the tether member); ratchet tooth engagement portions 490 (of the outer shell member); button receiving aperture 491 (of the outer shell member); elastomer ball receiving aperture 492. The elastomer ball is preferably made of viton.

The fuel cap controls vapor emissions by a system of valves. The intake valve allows ambient atmosphere into the tank to replace the volume of fuel consumed by the motor the intake valve doesn't allow vapors to escape. The exhaust valve will allow vapors to pressurize up to 5 PSI and release into the atmosphere above 5 PSI. The manual release valve allows the user to relieve any built up pressure in the tank to connect or disconnect fuel hoses, remove the cap, etc., safely without spraying or spilling liquid fuel. The cap contains a ratcheting feature to give the user an audible and tactile indication that the cap is seated and sealed properly on the tank. The tether assembly protects the valves from direct contact with liquid fuel due to splashing within the tank. Cap design is such that any vapors released through the bottom of the cap to minimize exposure to the user. The manual release valve is normally closed unless pressure is applied by the user. When the user removes the pressure to the button, it automatically releases and allows the valve to close using 2 sets of springs.

As shown in FIG. 5, second spring 464 maintains manual release button member 468, and its elastomer ball prod portion 470, in a raised position spaced away from elastomer ball 462. In this raised position, flange 472 is pushed up against the edge of button receiving aperture 491 (see FIG. 11) so that the tank, and its vapor space, is sealed in a pressure tight fashion so longs as no user is manually releasing by pressing down on the release button.

When a user does press down on the exposed top of the release button member (in the direction of arrow P), then the button member and flange its flange are forced down to a lowered position against the bias of second spring 464 and first spring 460. In the lowered position, the vapor space comes into fluid communication with the external atmosphere. If there is a positive pressure in the vapor space, the vapor can escape through the space between the flange of the button member and the edge of the button receiving aperture. If there is negative pressure, then atmospheric air will be sucked into the vapor space in the opposite direction over the same air communication path.

When the manual release button is forced down to the lowered position, the venting path for air communication is shown by the thick, red, dotted curve as shown in FIG. 5. In the FIG. 5 view, some portions of the dotted curve lie within the cross sectional profile of button member 468 itself. This is possible because, as best shown in FIG. 6, the button member has defined therein first slot channels 466; second slot channels 474; and a cruciform shaped elastomer ball prod portion 470. These slot channels, and the channels effectively formed by the cruciform prod allow air to travel within the interior space of the button member between the vapor space and the exterior atmosphere. In order for the air communication path shown in FIG. 5 to remain open: (i) flange 472 must be pushed down and away from button receiving aperture 491; and (ii) elastomer ball prod portion 470 must be sufficiently pushed down to prod elastomer ball 462 down and away from engagement with elastomer ball receiving aperture 492. When a user releases the button member, then first spring 460 forces elastomer ball 462 back up against elastomer ball receiving aperture to block the air communication path shown in FIG. 5 so that vapor space 406 is pressure-tight-sealed once again.

As best shown in FIGS. 7, 11 and 12, the ratchet teeth 475 and ratchet tooth engagement portions 490 face and engage in the radial direction R (see FIG. 12). This is different than conventional ratcheted designs where the teeth face and engage in a direction parallel to the axial direction defined by the central axis of rotation of the fuel cap.

As best shown in FIGS. 8-10, the tether-to-cap securing portion 480 of tether member 408 c snap fits into tether engagement slot 476. Tethering leash portion: (i) extends into the interior space of the fuel tank when the fuel cap is secured to close the fuel tank; and (ii) extends out of the fuel tank to tether the fuel cap when the fuel cap is opened. Anchor portion 482 is shaped to prevent the tether member from being completely removed from the fuel tank so that fuel cap remains tethered even when it is away from the vicinity of the opening in the fuel tank through which additional fuel is introduced. One thing to note about the design of tether member 408 c is that it is preferably a single piece of a single material. This is preferable to conventional rope tethers that anchored in interior space of the fuel tank (like the design of FIGS. 8 to 10), but are made up of multiple piece parts because the material that is used to make the rope is generally not suitable to secure the tether to the cap or to make an anchor. This is also preferable to any conventional designs that may anchor, or otherwise be secured to, a location outside of the fuel tank because extra hardware will be required to make this securement because these externally secured designs do not use the fuel opening itself to restrain the tether on the fuel tank side.

The tether design of FIGS. 8 to 10 will generally not provide a tether that is as flexible as a conventional rope style tether. However, the tether needs to be relatively flexible, and is preferably sufficiently flexible so that the weight of the fuel cap will bend the tether downwards so that the fuel cap will lean down against the side of the tank when the cap is removed from the tank. This flexibility can be achieved by carefully choosing: (i) the material of the single piece tether member; and (ii) the tether cross sectional area and profile. Preferably, the single piece tether of the present invention is made of a gasoline resistant polymer. One currently-preferred material is acetal.

The fuel cap assembly of FIGS. 13 to 23 is believed to have lower tooling costs than the fuel cap assembly embodiment 408 discussed above in connection with FIGS. 5 to 12. FIGS. 13 to 22 show fuel cap assembly 500, including: outer shell 502; shunt value safety seal 504; manual release button ring 506; viton ball 508; spring 510; spring retainer 512; inner cap 514; intake value 516; exhaust value 518; gasket 520; tethered assembly 522; tether 524; button guard 526; alignment hole 528; inserts 530; snap attachment for tether 532; vent hole 534; spin or sonic weld 536; gasket seal 538; snap portion 540; ridges portion 542; contour portion 544; seal seat 546; inside threads for exhaust valve 548; hole for exhaust value feature 550; inner threads for tank 552; ring support post 554; intake hole 556; exhaust valve seal feature 558; voided outer threads 559; five psi valve 560; and manual release feature 562.

As shown in FIG. 15, inserts 530 in the hole in the inner shell move the viton ball down against the spring.

As shown in FIG. 18: (i) snap portion 540 snaps into tethered assembly part 522; (ii) ridges portion 542 render the tether somewhat flexible so that it will hang downwards over the side of the vehicle and out of the way when a user is refilling the fuel tank; and (iii) contour portion 544 is contoured to match the interior of the fuel tank opening.

As shown in FIG. 19: (i) seal seat 546 should preferably be capable of reliably holding 20 psi of pressure when twisted down; and (ii) inside threads for exhaust valve 548 match voided threads on exhaust valve feature of the inner cap.

As shown in FIG. 21: ring support post 554 supports the manual release ring; (ii) intake hole 556 may not be needed in all embodiments of the present invention; (iii) spring retainer 512 may be a snap piece or it may be sonically welded.

DEFINITIONS

Any and all published documents mentioned herein shall be considered to be incorporated by reference, in their respective entireties, herein to the fullest extent of the patent law. The following definitions are provided for claim construction purposes:

Present invention: means at least some embodiments of the present invention; references to various feature(s) of the “present invention” throughout this document do not mean that all claimed embodiments or methods include the referenced feature(s).

Embodiment: a machine, manufacture, system, method, process and/or composition that may (not must) meet the embodiment of a present, past or future patent claim based on this patent document; for example, an “embodiment” might not be covered by any claims filed with this patent document, but described as an “embodiment” to show the scope of the invention and indicate that it might (or might not) covered in a later arising claim (for example, an amended claim, a continuation application claim, a divisional application claim, a reissue application claim, a re-examination proceeding claim, an interference count); also, an embodiment that is indeed covered by claims filed with this patent document might cease to be covered by claim amendments made during prosecution.

First, second, third, etc. (“ordinals”): Unless otherwise noted, ordinals only serve to distinguish or identify (e.g., various members of a group); the mere use of ordinals shall not be taken to necessarily imply order (for example, time order, space order).

Mechanically connected: Includes both direct mechanical connections, and indirect mechanical connections made through intermediate components; includes rigid mechanical connections as well as mechanical connection that allows for relative motion between the mechanically connected components; includes, but is not limited, to welded connections, solder connections, connections by fasteners (for example, nails, bolts, screws, nuts, hook-and-loop fasteners, knots, rivets, quick-release connections, latches and/or magnetic connections), force fit connections, friction fit connections, connections secured by engagement caused by gravitational forces, pivoting or rotatable connections, and/or slidable mechanical connections.

To the extent that the definitions provided above are consistent with ordinary, plain, and accustomed meanings (as generally shown by documents such as dictionaries and/or technical lexicons), the above definitions shall be considered supplemental in nature. To the extent that the definitions provided above are inconsistent with ordinary, plain, and accustomed meanings (as generally shown by documents such as dictionaries and/or technical lexicons), the above definitions shall control.

Unless otherwise explicitly provided in the claim language, steps in method steps or process claims need only be performed in the same time order as the order the steps are recited in the claim only to the extent that impossibility or extreme feasibility problems dictate that the recited step order be used. This broad interpretation with respect to step order is to be used regardless of whether the alternative time ordering(s) of the claimed steps is particularly mentioned or discussed in this document—in other words, any step order discussed in the above specification shall be considered as required by a method claim only if the step order is explicitly set forth in the words of the method claim itself. Also, if some time ordering is explicitly set forth in a method claim, the time ordering claim language shall not be taken as an implicit limitation on whether claimed steps are immediately consecutive in time, or as an implicit limitation against intervening steps. 

1. A fuel tank assembly comprising: a fuel tank defining an interior space; a passive vent that is movable between: (i) an open position that opens a first air communication path between the interior space of the fuel tank and the external atmosphere, and (ii) a closed position that closes the first air communication path; and an active pressure equalization hardware that automatically and selectively opens at least a second air communication paths in response to a pressure difference between the interior space of the fuel tank and the eternal atmosphere.
 2. The assembly of claim 1 wherein the passive vent comprises biasing hardware shaped, located and/or connected to bias the passive vent sub-assembly to its closed position.
 3. The assembly of claim 1 wherein the active pressure equalization hardware comprises an air intake valve shaped, structured and located to automatically and selectively open the second air communication path between the interior space of the fuel tank and the external atmosphere when the negative relative pressure in the interior space of the fuel tank increases in magnitude above a threshold negative pressure.
 4. The assembly of claim 1 wherein the active pressure equalization hardware comprises a vapor exhaust valve shaped, structured and located to automatically and selectively open the second air communication path between the interior space of the fuel tank and the external atmosphere when the positive relative pressure in the interior space of the fuel tank increases in magnitude above a threshold positive pressure.
 5. The assembly of claim 1 wherein the active pressure equalization hardware comprises: an air intake valve shaped, structured and located to automatically and selectively open the second air communication path between the interior space of the fuel tank and the external atmosphere when the negative relative pressure in the interior space of the fuel tank increases in magnitude above a threshold negative pressure; and a vapor exhaust valve shaped, structured and located to automatically and selectively open a third air communication path between the interior space of the fuel tank and the external atmosphere when the positive relative pressure in the interior space of the fuel tank increases in magnitude above a threshold positive pressure.
 6. The assembly of claim 5 further comprising a fuel cap sub-assembly comprising a removable fuel cap, wherein the passive vent, the air intake valve and the vapor exhaust valve are all built into the fuel cap.
 7. The assembly of claim 1 further comprising a fuel cap sub-assembly comprising a removable fuel cap, wherein the passive vent and the active pressure equalization hardware are built into the fuel cap.
 8. A fuel cap assembly comprising: a removable fuel cap comprising a first cap member and a second cap member; and fuel cap receiving hardware connected, shaped and/or located to removably engage the removable fuel cap; wherein: the removable fuel cap defines a central axis, an axial direction, an angular direction and a radial direction; the removable fuel cap and fuel cap receiving hardware are connected, shaped and/or located so that the removable fuel cap is removed by turning it in the angular direction and translating it in the axial direction; the first cap member comprises a plurality of ratchet teeth; the second cap member comprises at least one ratchet tooth engaging member; and the plurality of ratchet teeth face and engage with the at least one ratchet tooth engaging member in the radial direction.
 9. The assembly of claim 8 wherein: the first cap member is an inner shell member; and the second cap member is an outer shell member that fits around the inner shell member at least substantially around the angular direction.
 10. A fuel cap assembly for use with a fuel tank, the fuel cap assembly comprising: a fuel cap; and a tether member made of a single piece of a single material; wherein: the tether member comprises a cap-securement portion that is shaped, sized and/or located to be mechanically secured to the fuel cap; the tether member further comprises a tethering portion that is shaped, sized and/or located to: (i) be accommodated within an interior space of the fuel tank when the fuel cap is engaged to seal the fuel tank, and (ii) to tether the fuel cap at location(s) spaced apart from a fueling opening in the fuel tank when the fuel cap is removed from the fuel tank for fueling; and the tether member further comprises an anchor portion sized, shaped and/or located to be held within the interior space of the fuel tank, and prevented by physical interference from exiting the interior space of the fuel tank through the fueling opening. 